Guitars and other stringed instruments are designed to accommodate a particular type of string. Classical guitars, for example, have a relatively large body with a thin top, scale length, neck width, bracing, and other characteristics suitable for gut or nylon strings. Steel string guitars generally have more leeway in overall design, but must have a stronger bracing system to adequately tension the strings. Of course, the sound varies enormously from instrument to instrument, with classical instruments generally providing soft, warm tones, and steel string instruments generally having brightness and clarity characteristic of metallic strings.
From time to time musicians have thought it desirable to provide completely different types of sounds from a single instrument. To that end it is known to employ two different sounding boards with a single set of strings. U.S. Pat. No. 3,633,452 to Beasley, for example, uses a single set of strings in conjunction with a special bridge that activates either guitar or banjo sounding boards. U.S. Pat. No. 3,633,452, as well as all other cited references, are incorporated herein by reference in their entirety.
It is also possible to use strings of different types in an instrument with only a single sounding board. One way to achieve that result is to provide two necks, each with its own set of strings. U.S. 20030159562 to Bailey (publ. Aug. 28, 2003), for example, discloses a guitar with two necks connected to a single body. The problem there, of course, is that the instrument becomes quite unwieldy.
Another possibility is to simply mismatch the strings. Thus, a musician may substitute a single nylon string among a set of gut strings. But the effect is problematic because in a typical instrument one would be merely replacing sounds rather than adding sounds. One could, of course, mismatch strings on an instrument with a large number of strings, but the mechanics are problematic. Thus, a 12 string solid body guitar could be strung with a lower register of nylon strings and a higher register of steel strings. But such a guitar would not adequately produce the sounds of the non-metallic strings. A conventional 12 string acoustic could be used, but the bracing required for 12 steel strings is too substantial to permit the top to be activated sufficiently by the lower tension nylon strings. In addition, a standard bridge for a 12 string guitar would be inadequate because it would not provide sufficient separation of the two registers of strings, either acoustically or electronically.
There are numerous bracing designs that provide superior strength using transverse braces and a central fan brace. Several of these have been patented or are patent pending, see e.g., WO 9416430 to Nieminen (publ. July 1994), U.S. Pat. No. 4,084,475 to Horowitz (April 1978), and U.S. Pat. No. 6,169,236 to Pilar et al. (January 2001). Unfortunately, those bracing systems are deemed to provide either insufficient strength, or to provide sufficient strength at the cost of detrimental effects on the sound produced.
Thus, there is a need for a musical instrument that has at least two registers of strings, and a bridge that separates the sounds of the different registers. There is a further need for a new bracing system in a hollow body guitar, which provides sufficient strength to handle full sets of both metallic and non-metallic strings, without unduly negative impact on the sound.